Building for Production

Overview

Building UNS for production involves two main steps:

Compile the Python backend into a standalone binary
Package the Electron app with electron-builder

The final distributable includes the React frontend, Electron runtime, and Python engine bundled together.

Build times vary by platform. Expect 2-5 minutes for a full build on modern hardware.

Build Architecture

The production build structure:

UNS.app / UNS.exe / UNS
├── Electron App (ASAR)
│   ├── main.js
│   ├── preload.js
│   └── frontend/dist/       (React build)
└── Resources/bin/
    └── engine               (Python binary)

The Python engine is placed in the app’s resource directory and launched by Electron at runtime.

Building the Python Engine

The Python backend must be compiled before building the Electron app.

Activate Virtual Environment

cd backend
source venv/bin/activate

Always activate the venv before running PyInstaller. Otherwise, it may fail to bundle dependencies.

Run PyInstaller

Compile the FastAPI app into a standalone binary:

python -m PyInstaller --onefile --windowed --name engine api.py

Flags explained:

--onefile - Bundles everything into a single executable
--windowed - Suppresses console window (important for desktop apps)
--name engine - Names the output binary “engine” (or “engine.exe”)

Output location: backend/dist/engine

Verify the Binary

Test the compiled engine manually:

cd dist
chmod +x engine  # macOS only
./engine /tmp/test_output

You should see:

🚀 Engine starting... Data home: /tmp/test_output
INFO:     Started server process
INFO:     Uvicorn running on http://127.0.0.1:8000

Press Ctrl+C to stop it.

Use engine.spec for Faster Rebuilds

PyInstaller generates engine.spec on the first run. Use it for faster subsequent builds:

python -m PyInstaller engine.spec

This skips dependency analysis and uses cached data.

Troubleshooting PyInstaller

ModuleNotFoundError in the binary

PyInstaller may miss some imports. Add them manually to engine.spec:

engine.spec

hiddenimports=[
    'fastapi',
    'uvicorn.logging',
    'uvicorn.loops.auto',
    'ebooklib.epub',
],

Binary is too large (>100MB)

This is normal for Python apps. The binary includes:

Python runtime
All pip packages (FastAPI, Uvicorn, ebooklib, etc.)
Standard library modules

To reduce size, use --exclude-module for unused packages:

--exclude-module matplotlib --exclude-module numpy

macOS Gatekeeper blocks the binary

Sign the binary with an Apple Developer certificate or instruct users to:

Right-click the app → Open
Go to System Preferences → Security & Privacy
Click Open Anyway

Building the Electron App

Once the Python engine is compiled, build the full desktop app.

Build the Frontend

From the project root:

npm run build:frontend

This runs:

cd frontend && npm install - Ensures dependencies are installed
npm run build - Builds React app with Vite

Output: frontend/dist/ (HTML, CSS, JS)

Package with Electron Builder

Build the platform-specific installer:

npm run build:electron

Output directory: dist_electron/

Full Build (One Command)

To build everything at once:

npm run build

This runs:

npm run build:frontend
npm run build:electron

This does NOT rebuild the Python engine. You must rebuild backend/dist/engine separately if you changed api.py.

Platform-Specific Builds

macOS

Requirements:

macOS 10.13+ (to build)
Xcode Command Line Tools

Build targets:

dmg - Disk image installer (recommended)
pkg - macOS installer package
zip - Zipped app bundle

Build command:

npm run build:electron -- --mac dmg

Output:

dist_electron/UNS-1.1.0.dmg
dist_electron/mac/UNS.app (unpacked)

Code signing (optional):

package.json

"build": {
  "mac": {
    "identity": "Developer ID Application: Your Name (TEAM_ID)",
    "hardenedRuntime": true,
    "gatekeeperAssess": false,
    "entitlements": "build/entitlements.mac.plist"
  }
}

Windows

Requirements:

Windows 7+ (to build)
Node.js with build tools

Build targets:

nsis - NSIS installer (default)
portable - Portable executable
zip - Zipped app

Build command:

npm run build:electron -- --win nsis

Output:

dist_electron/UNS Setup 1.1.0.exe
dist_electron/win-unpacked/ (unpacked)

Code signing (optional):

package.json

"build": {
  "win": {
    "certificateFile": "path/to/cert.pfx",
    "certificatePassword": "your-password",
    "signingHashAlgorithms": ["sha256"]
  }
}

Linux

Requirements:

Linux (any distro)
Build essentials installed

Build targets:

AppImage - Universal Linux package (recommended)
snap - Snap package
deb - Debian/Ubuntu package
rpm - RedHat/Fedora package

Build command:

npm run build:electron -- --linux AppImage

Output:

dist_electron/UNS-1.1.0.AppImage
dist_electron/linux-unpacked/ (unpacked)

electron-builder Configuration

The build configuration is in package.json:

package.json

{
  "build": {
    "appId": "com.universalnovelscraper.app",
    "productName": "UNS",
    "directories": {
      "output": "dist_electron"
    },
    "files": [
      "main.js",
      "preload.js",
      "assets/icon.png",
      "frontend/dist/**/*"
    ],
    "asar": true,
    "extraResources": [
      {
        "from": "backend/dist",
        "to": "bin",
        "filter": ["engine", "engine.exe"]
      }
    ]
  }
}

Key settings:

files - What gets packaged in the ASAR archive
extraResources - Files placed outside ASAR (like the Python engine)
asar: true - Compresses app files for faster loading

Accessing the Engine Path

The engine location differs between development and production:

main.js

const isPackaged = app.isPackaged;
const enginePath = isPackaged
  ? path.join(process.resourcesPath, 'bin', 'engine')
  : path.join(__dirname, 'backend', 'dist', 'engine');

const finalPath = (isPackaged && process.platform === 'win32') 
  ? `${enginePath}.exe` 
  : enginePath;

Environment	Path
Development	`<project>/backend/dist/engine`
Production (macOS)	`UNS.app/Contents/Resources/bin/engine`
Production (Windows)	`resources/bin/engine.exe`
Production (Linux)	`resources/bin/engine`

Common Build Issues

Engine binary not found in production

Check the extraResources config in package.json:

"extraResources": [
  {
    "from": "backend/dist",
    "to": "bin",
    "filter": ["engine", "engine.exe"]
  }
]

Ensure backend/dist/engine exists before building.

App crashes immediately after launch

Check if the Python engine starts correctly:
- Open the app
- Check Activity Monitor (macOS) or Task Manager (Windows)
- Look for a process named “engine”

Enable logging in main.js:

pythonProcess.stderr?.on('data', (data) => {
  console.error(`🐍 Python Error: ${data}`);
});

Run the app from terminal to see logs:

# macOS
./dist_electron/mac/UNS.app/Contents/MacOS/UNS

# Linux
./dist_electron/linux-unpacked/uns

# Windows
.\dist_electron\win-unpacked\UNS.exe

Build fails with 'Cannot find module'

Ensure all dependencies are installed:

npm install
cd frontend && npm install && cd ..
cd backend && pip install -r requirements.txt && cd ..

macOS: 'UNS is damaged and can't be opened'

This happens when the app isn’t code-signed. Users must:

Right-click → Open
Click “Open” in the security dialog

Or remove the quarantine flag:

xattr -cr /Applications/UNS.app

Windows: SmartScreen warning

Unsigned Windows apps trigger SmartScreen. Users should:

Click “More info”
Click “Run anyway”

To fix permanently, sign the app with an EV code signing certificate.

Testing the Build

Before distributing, test the packaged app:

Test Basic Functionality

Launch the app
Check if the UI loads
Navigate to Library, Download, History pages
Verify the Python engine is running (check Activity Monitor/Task Manager)

Test a Full Scrape

Add a provider (or use a pre-installed one)
Search for a novel
Start a download
Verify chapters are being scraped
Check if the EPUB is generated in the output folder

Test on a Clean Machine

The best test is on a machine without development tools:

No Node.js, Python, or dev tools installed
Fresh user account (no leftover config)
Different OS version (e.g., macOS 12 if you built on macOS 14)

Next Steps

Development Setup

Return to setup guide for development mode

Project Structure

Learn about the codebase organization

Getting Started

Core Features

Advanced Usage

Architecture

Developer Guide

Help

Overview

Build Architecture

Building the Python Engine

Troubleshooting PyInstaller

Building the Electron App

Platform-Specific Builds

macOS

Windows

Linux

electron-builder Configuration

Accessing the Engine Path

Common Build Issues

Testing the Build

Next Steps

Development Setup

Project Structure

Build docs developers (and LLMs) love

Getting Started

Core Features

Advanced Usage

Architecture

Developer Guide

Help

​Overview

​Build Architecture

​Building the Python Engine

​Troubleshooting PyInstaller

​Building the Electron App

​Platform-Specific Builds

​macOS

​Windows

​Linux

​electron-builder Configuration

​Accessing the Engine Path

​Common Build Issues

​Testing the Build

​Next Steps

Development Setup

Project Structure

Build docs developers (and LLMs) love

Overview

Build Architecture

Building the Python Engine

Troubleshooting PyInstaller

Building the Electron App

Platform-Specific Builds

macOS

Windows

Linux

electron-builder Configuration

Accessing the Engine Path

Common Build Issues

Testing the Build

Next Steps